单项选择题
A．learn how to do research and write papers B．have some learning experience C．learn about the course concretely and clearly D．know how to participate in discussions
A．how well they perform in class B．how carefully they prepare their lessons C．how fluently they express themselves in class D．how hard they work in and after class
A．after mid-1980s B．before mid-1980s. C．at the modern age D．in nowadays